Database Reference
In-Depth Information
STDDEV_SAMP(expression)
. The sample standard deviation.
VAR_POP(expression)
. The population variance, excluding null
values.
VAR_SAMP(expression)
. The sample variance, excluding null values.
COVAR_POP(expression, expression)
. The population covariance
of two expressions. The covariance is the average product of differ-
ences from two group means.
COVAR_SAMP(expression, expression)
. The sample covariance of
two expressions.
CORR(expression, expression)
. The coefficient of correlation of
two expressions. A correlation coefficient assesses the quality of a
least-squares fitting to the data. The least-squares procedure finds the
best-fitting curve to a given set of values.
REGR_[ SLOPE | INTERCEPT | COUNT | R2 | AVGX| AVGY |
SXX | SYY | SXY ](expression, expression)
. Linear regression func-
tions fit a least-squares regression line to two expressions. Linear
regression is used to make predictions about a single value. Simple
linear regression involves discovering the equation for a straight line
that most nearly fits the given data. The discovered linear equation is
then used to predict values for the data. A linear regression curve is a
straight line through a set of plotted points. The straight line should
get as close as possible to all points at once.
. This function calculates Pearson's correlation
coefficient, measuring the strength of a linear relationship between
two variables. Plotting two variables on a graph results in a lot of dots
plotted from two axes. Pearson's correlation coefficient can tell you
how good the straight line is.
CORR_{S | K}
. A median is a middle or interpolated value. A
median is the value literally in the middle of a set of values. If a distri-
bution is discontinuous and skewed or just all over the place, then the
median will not be anywhere near a mean or average of a set of values.
A median is not always terribly useful.
MEDIAN
STATS_{BINOMIAL_TEST | CROSSTAB | F_TEST |
KS_TEST | MODE | MW_TEST | ONE_WAY_ANOVA |
STATS_T_TEST_* | STATS_WSR_TEST}
. These functions provide
various statistical goodies. Explaining what all of these very particular
statistics functions do is a little bit more of statistics than Oracle SQL
for this topic.
